ELECTRICAL ACTIVITY IN RESPONSE TO LIGHT OF THE OCELLUS OF THE HYDROMEDUSAN,SARSIA TUBULOSA

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Abstract
The electroretinogram (ERG) recorded from the ocellus of Sarsia tubulosa has a characteristic positive potential change at the onset of illumination, followed by a slower biphasic pulse and a positive deflection at the cessation of illumination succeeded by high-frequency pulses. The amplitude of initial pulse is graded with respect to changes in intensity and wavelength of the light stimulus. The maximum spectral sensitivity lies around 540 nm. Responses to light with opposite polarity were recorded from the optic ganglion which surrounds the ocellus. Differences in response patterns inside and outside the receptive field of the ocellus were mapped. Morphological structures which could give rise to component responses of the ERG and its neuronal pathway are discussed.